Sequences near the termini are required for transposition of the maize transposon Ac in transgenic tobacco plants.

Abstract

Deletion derivatives of the maize transposable element Activator (Ac) were constructed in vitro and inserted into a kanamycin resistance gene. These constructions were then introduced into tobacco protoplasts derived from plants previously transformed with Ac. The ability of each deletion derivative to excise was measured by whether or not kanamycin-resistant tobacco calli were recovered. This allowed us to determine the length ofDNA present at each terminus that is required to respond to the products expressed by the Ac element present in the genome. We show that around 200 base pairs (bp) are required at both ends for excision to occur at wild-type levels. When between 100 and 200 bp were retained at one of the ends, reduced frequencies of excision were detected. With less than 100 bp remaining at either end, no excision was detected. In addition, we show that although similar lengths of DNA are required at each terminus, the termini are not interchangeable. The significance of these data is discussed with respect to the protein(s) which interact(s) with the termini of Ac.

Abortive Gap Repair: Underlying Mechanism for Ds element Formation

“…It encodes an 807-amino-acid protein, the transposase, necessary for both Ac and Ds transposition (28). Ds elements, on the other hand, do not encode a functional transposase but retain regions which are essential for their transposition (6). There are six fully sequenced Ds elements, all of which share with Ac nearly identical TIRs and fall into the following four categories: (i) those with nearly no similarity to Ac, like Ds1 (57); (ii) elements with highly similar subterminal regions but with internal deletions, like Ds9 (46); (iii) double Ds elements where one internally deleted Ds is inserted into another identical Ds in an inverted orientation (9); and (iv) Ds elements that contain both deletions and insertions in the internal part of the element, like Ds2 (40) and the Ds element in WxB4 (60).…”

Transposase binding site methylation in the epigenetically inactivated Ac derivative Ds‐cy

“…Of the seven most internally located TPase binding sites (residues 165-235), five point into the same direction as the terminal group. These sites are of similar importance as the most terminal ones, as their deletion reduces transposition frequency to 10-20% (Coupland et al, 1989).…”

A system for insertional mutagenesis and chromosomal rearrangement using the Ds transposon and Cre—lox

“…In addition, the 3' terminus of tr-Ds/ox 'B' had sustained a 4 bp deletion. We expect that these deletions would prevent the 'A' and 'B' tr-Dsloxs from excising (Coupland et al, 1989;Hehl and Baker, 1989). Neither of these 2 Dslox insertions were flanked by the 8 bp direct duplication characteristic of Ac and Ds insertion (Muller-Neumann et al, 1984;Pohlman et al, 1984;Sutton et al, 1984).…”